الملخص

Abstract The histological sections of the nervous system of Ascaridia galli stained with toludine blue, showed that it consists of a nerve ring surrounding the oesophagus known as circumenteric ring which in turn connected with a number of ganglia namely: pair of lateral ganglia, ventral ganglia, small dorsal ganglion, pair of subdorsal ganglia, pair of post–lateral ganglia and a pair of postero–ventral ganglia. This ring situated obliquely at a distance of 0.7 (0.65- 0.8) mm from the anterior tip of the worm and formed mainly from fibers and small number of gangliotic cells. From the cephalic ganglia 6 papillary nerves arise in the anterior region to innervate the sense organs situated at the anterior region. From this circumenteric ring also a number of main nerves arise and extend posteriorly namely :mid dorsal, two pairs of lateral and a mid -ventral. The two ventrals end in the posterior region of the body in a pair of large ganglia near the anus known as lumbral ganglia. The mid– ventral nerve cord considered the most prominent and has a number of ganglia arise from the ganglia ventral side. Furthermore there is two enteric or sympathetic systems, one is anterior near the esophagus and the other near the rectum. There are three types of sense organs: cephalic, cuticular and caudal. Cephalic sense organs include 12 structures in the anterior region, cuticular include those situated between the head and the tail ,and the caudal include two types of caudal sense organs and a pair of phasmids.